WinRadio CMC common mode choke. 30

[BOBRR]

Hello, Anyone using that WinRadio Receiving only
common mode choke CM 30. ?

Effective ? Caveats ?
Thoughts on ?

What’s the lower freq. limit ?

Thanks,
Bob

 

[kruser]

Hello, Anyone using that WinRadio Receiving only
common mode choke CM 30. ?

Effective ? Caveats ?
Thoughts on ?

What’s the lower freq. limit ?

Thanks,
Bob

Specs show the freq range from DC to 30 MHz so the lower limit is basically as low as you can go. I've never used their choke before so I can't answer your question as to its effectiveness.

WiNRADiO WR-CMC-30 Common-Mode Choke

 

[BOBRR]

Hello,

This is "a bit more" on CMC that I posted yesterday:

Came across a gadget I had ordered, and never used, some years ago.

Would like to learn a bit more about it.

It's a Common Model Choke from the WinRadio folks.
Model: CMC-30

Anyone using ?

*What's "likely" inside ? (can't open case).
They say the response is dc to 30 MHz, but this can't be true, can it ?
If a trans. or toroid, there is likely the typical low freq. rolloff ?

Why do they say to ground it ?

I do receiving only; long wire ant. outside, a UnUn, and a coax run to house.
Be a bit of a pain hooking it up, even at radio end.
Think it's worth doing ?

Any thoughts on this would be most appreciated.

Thanks,
Bob

 

[prcguy]

Hello,

This is "a bit more" on CMC that I posted yesterday:

Came across a gadget I had ordered, and never used, some years ago.

Would like to learn a bit more about it.

It's a Common Model Choke from the WinRadio folks.
Model: CMC-30

Anyone using ?

*What's "likely" inside ? (can't open case).
They say the response is dc to 30 MHz, but this can't be true, can it ?
If a trans. or toroid, there is likely the typical low freq. rolloff ?

Why do they say to ground it ?

I do receiving only; long wire ant. outside, a UnUn, and a coax run to house.
Be a bit of a pain hooking it up, even at radio end.
Think it's worth doing ?

Any thoughts on this would be most appreciated.

Thanks,
Bob

For a feedline common mode choke you want to know how much resistive choking impedance they have or how much isolation they provide at your frequency of interest. Most companies or garage shops don't mention this or don't have the equipment to measure it or simply don't know what it is. I would avoid any common mode choke that doesn't publish their measured specs. WinRadio mentions what the internal inductance is and that's nice but not really useful.

A simple common mode choke might be some ferrite beads slipped over a length of coax and the ferrite type and number of beads will determine the isolation and choking impedance at various frequencies. These types of chokes can reach about 20dB isolation at some frequencies and less at others. Its usually the lower freqs that suffer where the choke might reach 20dB isolation in the 10-15MHz range then it rolls off to maybe 10dB at 10m and 80m then 160m it barely reaches 5dB isolation.

A better choke is made by wrapping a specific amount of turns of coax around and through a ferrite toroid. These can reach about 30dB isolation and a little broader frequency range. A single toroid type might be 30dB isolation in the 10-15MHz range and 20dB at 10m and 80m and maybe 10dB at 160m. You can vary the ferrite mix and number of turns to target different frequency ranges.

Some newer designs will use multiple ferrite cores with multiple windings in series with each other and the cores may be of different ferrite types to target different frequency ranges and the result of placing then in series adds more isolation. Some of these types can reach over 40dB isolation over much of the HF range and still have 20-30dB isolation at the frequency extremes.

I suspect the WinRadio thing might be a ferrite rod with some miniature coax wrapped around it then a metal shield you can ground. It would probably have some choking impedance and isolation at some frequencies, but nothing like some of the later designs on the market. Some of the best designs and specs I've found are from MyAntennas and Palomar Engineers, although I'm convinced Palomar copied MyAntennas on their Maxi-Choker series. I was at a gathering with Bob from Palomar Engineering and mentioned the MyAntennas CMC-130-3K choke and its impressive specs and asked why Palomar didn't have anything that good. About 6mo later Palomar came out with the Maxi-Choker with similar design, specs and price. Here is a link to both and these are about the end of the line highest performing common mode chokes out there.

CMC-130-3K 1-30MHz – MyAntennas.com

MAXI-CHOKER Coax Line Isolator/Choke, 1-61 MHz, 3KW, up to -48Db Common Mode Rejection - Common Mode Noise Filter - Coax - Palomar Engineers®

MAXI-CHOKER Features: - Uses proprietary Multi-Mix, Multi-Core, Multi-Turn(TM) ferrite technology for maximum choking (up to -48 dB common mode noise rejection) and maximum bandwidth - 3 KW PEP, 50 ohm SO-239 connectors In/Out, 1-61 MHz - Suppresses transmitter coax feed line radiation when…

palomar-engineers.com